CLOUD COMPUTING FOR MOBILE USERS: CAN OFFLOADING COMPUTATION SAVE ENERGY? . Karthik Kumar and Yung-Hsiang Lu, Purdue University Presenter Yifei Sun. What cloud gives us, generally. Take Amazon cloud for example. store personal data (Simple Storage Service (S3) )
Karthik Kumar and Yung-Hsiang Lu, Purdue University
Presenter Yifei Sun
Take Amazon cloud for example.
(Simple Storage Service (S3) )
(Elastic Compute Cloud (EC2). )
If you want to set up a business.
Two main concerns:
Various studies have identified longer battery
lifetime as the most desired feature of such
How to implement a quantitative study. The amount of energy saved is
S : the speed of cloud to compute C instructions
M : the speed of mobile to compute C instructions
D : the data need to transmit
B : the bandwidth of the wireless Internet
the energy cost per second when the mobile phone is doing computing
the energy cost per second when the mobile phone is idle.
the energy cost per second when the mobile is transmission the data.
Suppose the server is F times faster—that is, S
= F × M. We can rewrite the formula as
Energy is saved when this formula produces a
positive number. The formula is positive if D/B
is sufficiently small compared with C/M and F
is sufficiently large.
A chessboard has 8 × 8 = 64 positions. Each
player controls 16 pieces at the beginning of
the game. Each piece may be in one of the 64
possible locations and needs 6 bits to
represent the location. To represent a chess
game’s current state, it is sufficient to state
that 6 bits × 32 pieces = 192 bits = 24 bytes;
this is smaller than the size of a typical
The amount of computation for chess is very
large; Claude Shannon and Victor Allis
estimated the complexity of chess to exceed
the number of atoms in the universe. Since the
amount of computation C is extremely large,
and D is very small, chess provides an example
where offloading is beneficial for most wireless
In these cases,
where the value of B in Equation can become
very small or even zero, cloud computing does
not save energy.
There is a fundamental assumption
under-lying this analysis with the client-server
model: Because the server does not already
contain the data, all the data must be sent to
the service provider.
However, cloud computing changes that
assumption: The cloud stores data and performs
computation on it. For example, services like
Amazon S3 can store data, and Amazon EC2 can
be used to perform computation on the data
stored using S3.
Another possible privacy and security solution
is to use a technique called steganography :
have significant redundancy. This makes it
possible to hide data in multimedia using
transform the data before storage so that
operations can still be performed on the data.
Performing encryption or steganographic
techniques before sending data to the cloud
requires some additional processing on the
mobile system. So the formula become:
for mobile users.
efficient when migrated to the cloud.
significantly different from cloud services for
desktops because they must offer energy
overhead for privacy, security, reliability,
and data communication before offloading.